How to open a document stored in Object Storage from Salesforce?

I am working on a project where PDFtron could be really useful. We have tons of files that we are planning to move to any object storage (S3, Wasabi, Azure). I want this files to be accessible in Salesforce, so users can edit, update, annotate. I did look into PDFtron’s guide on “How to open document stored in Salesforce” but that was not helpful enough since we are planning to store files in external object storage and access it in Salesforce. My question is, How can I open document in Salesforce that is stored in external object storage?

Thank you for reading my comment and for your time on the issue. Thank you!